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011/! imam Reissued Nov. 24, 1931 UNITED STATES PATENT OFFICE can. A. FRAHM AND EDMUND w; mnmnnscnnnrnna, or cannon, omo, assrcnons r 'rnnnmon METAL MANUFACTURING COMPANY, or can'ron, onro, a conrona men or 01:10

snnn'r METAL snnr'r Original application filed January 25, 1928, Serial N0. 249,353. Divided and application filed February 13, 1928, Serial No. 253,948. Original No. 1,789,972, dated January 27, 1931.

filed July 16, 1931. Serial, No. 551,270.

The invention relates to hollow shafts made of metal rolled into sheets, strips or plates, and adapted for use in columns and as pillars, posts, poles, standards and thellke;

5 including shafts of this character which are corrugated or fluted to increase the strength of the same, as shown in the Numan Patents No. 838,571 of December 18, 1906, and No. 888,114 of May 19, 1908.

v The present application is a continuation in part of the common subjectmatter set forth in the applications of Garl A. Frahm, filed September 9, 1926, Serial No. 134,394, and of Edmund W. Riemenschneider, filed December 30, 1926, Serial No. 157,981; and this application is a division of our parent application for patent for improvements in sheet metal shafts and method of making same, filed January 25, 1928, Serial No. 249.353, matured in Letters Patent No.

1,777,080, dateil September 30, 1930; and the object of the present improvement is to increase the strength of shafts of this character when made of rolled metal sheets, strips or plates, hereinafter referredto collectively as sheet metal; and the general object of the present improvement is to producea sheet metal shaft having a greater strength against compressing, bending, flexing and tortional shaft being especially adapted for use as telegraph, telephone, transmission or trolley poles, having greater strength and being lighter in weight and neater in appearance than poles at. present in use for such purposes. i

In the manufacture of fluted sheet metal shafts, the metal has been merely bent laterally over the ribs of a mandrel to form the fillets and fluts in the shaft, without changing the thickness of the sheet metal at any point, and without materially increasing the elastic limit of the metal beyond thenormal strength of the same in the sheet from which the shaft is made. 7,

Although sheet metal shafts made in this manner are strengthened to a certain extent by corrugations or flutesformed by bendingthe metal, it has been found in actual W practice and by tests, that when sub ected to strains than has heretofore been attained, the

application for reissue strains or blows, such shafts willinvariably bend or buckle inward more readily than similar shafts having sharp edged fillets between the flutes and by a mere bending of the sheet to form flutes or fillets, it has been commercially impossible to uniformly obtain an architecturally correct outline i'nthe shaft, or to produce the sharp corners or edges in the fillets which is essential in Doric and in Ionic or Corinthian columns; these 60. detrimental characteristics becoming more apparent and exaggerated as the thickness of sheet used is increased. v

Beginning with the formation of a tubular shaft, the present invention includes a'compression, as by cold rolling, of the sheet or plate metal wall of the shaft so .as to change the molecular arrangement of themetal and increase the elastic limit thereof.

Also, the formation of flutes and fillets by a swaging and flowing compression of the metal, as by cold rolling, which displaces the metal in certain places, forms sharp edges in the fillets and changes the molecular arrangement of the metal; so as to increase the strength of the fillets not only by an increased thickness of the metal, but by an increase in the elastic limit thereof in the region of the fillets.

Moreover, the compressing or cold rolling 8 operation straightens any longitudinal cainber or bends and any circular imperfections there may be in the contour of the tubular shaft, and sets the molecular arrangement of the metal in the same so that a finished shaft 55 may be split longitudinally and each half will hold its shape for matching and being readily joined to the other half, which cannot be done by a shaft formed merely by bending operations.

A fluting machine of the type set forth in the Frahm'Patent N0.1,605,628 of November 2, 1926, when properly modified and operated in the manner described in said parcut application, may he used in making the improved shaft, as illustrated in the accompanyingv drawingsforming part hereof, in which Figure 1 is a perspective view of a portion of a tapered tubular shaft from whicha fluted shaft may be made;

shaft of the Doric type, by cold rolling and extruding the metal for increasing the thickness at the angles and sharpening the same;

Fig. 7, a fragmentary enlarged section, showing details of an improved fillet of the Doric type; V

Fig. 8, a similar View of an ordinary fluted shaft of the Ionic or Corinthian order, made by the ordinary bending method;

Fig. 9, a similar view illustrating the method of making fillets in the improved shaft of the Ionic or Corinthian type, by cold rolling and extruding the metal for increasrolls and forming ing the thickness at the angles and sharpening the same; I

Fig. 10, a fragmentary enlarged section showing details of the improved fillet of the Ionic or Corinthian type; and

Fig. 11, a fragmentary transverse section through the mandrel and shaft, showing one manner of finishing the formation of the flutesb rolls.

Simi ar numerals refer to similar parts throughout the drawings.

When a tapered tubular shaft 14 the same may be formed from a tapered blank or strip of sheet or (plate metal by bending ice and edge welding means, as set forth in Riemenschneiders application for tubular column forming machine, filed August 30, 1926, Serial No. 132,- 369, matured in Letters Patent N 0. 1,7 65,384, dated June 24, 1930; and when so formed, the diameter of the tubular shaft may be and preferably is slightly larger than the diameterof the fillet forming ribs of the fluting mandrel, so as to give a circumferential fullness tobe taken up and trued by the cold rolling and flute forming operations, as shown in Fig. 2.

When the fluting operations are performed by a machine of the type shown in said Frahm Patent No. 1.605,828, the mandrel body 15 is provided with a series of equally spaced steel die bars or ribs 16 or 16a, extending radially from the periphery of the body, and each rib may be provided with a substantially V- shaped outer edge 16' or 16a for contact with the inner face of the tubular shaft. 14, as

shown in Figs. 6 and 9.

is used,

mass

-- The mandrel with the tubular shaft mounted thereon as shown in Fig. 2, is moved one or more times endwlse between a set or see ries of radi/ally yieldingrolls as 17 or 17a,

shaped to form the desired outline of the fillets to be formed and arranged to bear upon theshaft at' the points opposite corresponding die bars 16 or 160, as shown in Figs. 6 and 9. I y

There may be, and usually are required to be, two sets or series of such fillet forming rolls arranged to operate upon alternatefillets, because there is not room enough to place all the rolls in a single stand; and these rolls may be and preferably are provided with sharp angle V-shaped annular grooves 17 to produce the sharp edge fillets 18, as shown in Fig. 6, or may be provided with the flat bottom annular grooves 17a to produce the flat face fillets 19 with sharp edges 19, as shown in Fig. 9;

Suflicient pressure is applied to the fillet I forming rolls to displace or swage the metal in the fillets as the same passes through the rolls, and cause the metal to flow and -extrurle into the grooves of the rolls, to increase the thickness of the metal at that place and also lform a, sharp edge or sharp edges in the filets. I

The same operation cold rolls the metal in and adjacent to the fillets, and by changing the molecular arrangement of the same, increases its elastic limit and thereby increases the strength of the fillets as well as of the column, beyond that of a sheet metal column formed by merely bending the metal.

The same cold rolling operation also elongates the metal in the fillets and increases the length of the shaft to an extent which has and the metal therein being relatively softer than the cold rolled fillets, and being necessarily extended longitudinally by stretching to the extent of the increased length of the shaft, may also be stretched somewhat laterally 'in the formation of the flutes so as to slightly increase its elastic limit.

lVhereupon the mandrel with the fillet formed shaft thereon is passed one or more times between another set orseries of radial- 1y yielding rolls 20 and 20', shaped to form the desired concavity of the flutes and bearing upon the shaft at and between adjacent fi let forming die bars or ribs 16, as shown in Fig. 11.

The action of these rolls not only stretches and shapes the flutes, but completes the action of the fillet forming rolls and sets the molecular arrangement of the metal and relieves the same of flexing strains, so that the shaft will hold its shape thus given, even though it may be severed'longitudinally into two lateral halves.

Moreover, the same operations serve to straighten the tubularshaft longitudinally and to true its shape circumferentially, so that when the fluted shaft is removed longitudinally from the mandrel, it is a correctly formed and truely shaped straight shaft with sharp edge fillets of the type given to them by the fillet forming rolls.

The elongation of the shaftby the cold rolling 0 eration is accompanied by the taking up o the circumferential fullness of the same to such an extent that after the fillets have been formed as described, the shaft fits the mandrel so tightly that it is difficult if not impossible to remove the shaft from the mandrel until after the stretching action of the flute forming rolls, which acts to loosen the shaft from the mandrel, so as to permit an endwise removal therefrom.

It has been found by actual tests that sheet metal shafts formed and fluted by the improved method described herein, have a greater strength and agreater limit of elasticity than any other known form of tubular shafts of considerably greater weight made by merely bending the sheet metal; and at the same time the shaft is formed with clean cut sharp lines and with sharp edges on the fillets, thereby producing a shaft of architecturally correct outlines and appearance, which cannot be made by a bendin formation.

It has also been found liy actual tests that the increased thickness of the metal in the fillets, the extrusion of the metal in the sharp angles thereof, and the increased elastic limit of the metal in the region of the fillets, so greatly increases the ultimate strength of the improved shafts, over the strength of shafts fluted merely by bending, that they will bulge outward at a point of rupture andafter'rupture will stand a considerable loading, instead a of bulging inward under strain or impact at a point of rupture in the manner common to all other known types of tubular shafts.

It has not been found possible, heretofore, to make fluted shafts from the thicker gauges of rolled metal, from 11 gauge and thicker,

which are knownto the trade as plate metal;

because comparatively narrow'fillets between relatively wide flutes, cannot be formed merely by a bending operation, upon a small enough radius to give any substantial semblance to an architectural fluted column.

In addition to that inhibition, the inability to make a fluted shaft from plate metal, solely by a bending operation, is because the metal is so thick that a mere bending stretchc5 and reduces the thickness and may even rupture the metal itself, around the periphery of the fillet, so that, unless the same is accompanied by a swaging compression oper ation, such as is described herein, the shaft is weakened atthe very place it should be strengthened, for use as a column or pole.

I It is for these'reasons'that the swaging compressionmethod of making tubular shafts, described and claimed in said parent Patent No. 1,777,080, has rendered it possible, for' the first time, to make from plate metal, the tapered, fluted, tubular pole, which is described and claimed herein as a new artithe metal, but will also serve to strengthen the shaft b the resulting increase in the elastic limit 0 the metal.

Nor is it intended to limit the broad idea of compressing the metal with sufficient force to shape the fillets alone, or both the fillets and the flutes, and to swage anddisplace the metal in the fillets to cause it to flow and extrude av predetermined thickness and shape; to the cold rolling operations which are described herein for illustrating the preferred method of applying such pressure.

Nor is it intended to limit the scope of the invention to the tapered tubular shafts described herein by way of illustration, for obviously the broad idea of the improved method may be used as well for the production of tubular shafts without a taper, and to shafts having an entasis.

In the claims appended hereto, the expression sheet metal? is intended to include strips and plates as well as sheets of metal, and the term shaft is intended to include pillars, posts, poles, standards, columns and the like. r

We claim 2- 1. A tubular shaft formed with flutes and fillets made of sheet metal, the metal in the metal in the fillets having higher elastic limit than the metal in the flutes.

2. A tubular shaft formed with flutes and fillets made of sheet metal, the metal being thicker in the region ofthe fillets than else where.

3. A tubular shaft formed with flutes and fillets made of sheet metal, the thickness of the metal being greater in the fillets than in the flutes. 1

4. A tubular shaft formed with flutes and fillets made of sheet metal, the edges of the fillets being sharper than the edges of fillets formed merely by bending the metal.

5. A tubular shaft formed with flutes and fillets made of sheet metal, the thickness of the metal being greater in the fillets than in the flutes, and the edges of the fillets being sharper than the edges of fillets formed merely by bending the metal.

6. A tubular shaft formed with flutes and fillets made of sheet metal,-the thickness of t the metal being greater in the fillets than in the flutes, and the metal in the flutes having higher than the normal elastic limit inherent in filletsformed merely by bending the metal. 7. A tubular shaft formed with flutes and fillets made of sheet metal, the thickness of the metal being greater in the fillets than in the flutes, the metal in the fillets having higher than the normal elastic limit inherent in fillets formed merely by bending] the metal, and. the edges of the fillets being s arper than the edges of fillets formed merely by bending the metal.

8. A tubular shaft with flutes and fillets go made of sheet metal, in which the molecular arrangement of the metal in the region of the fillets is changed from the arrangement inherent in the sheet from which'it is made, and the elastic limit of the metal in the ;region of u the fillets is higher than the elastic limit inherent in said sheet when the fillets are made merel by bending the metal.

9. X tubular shaft formed with flutes and fillets made of sheet metal, in which the molecular arrangement of the metal in the fillets is changed from the arrangement inherent in the sheet from which it is made, and the elastic limit of the metal in the fillets is higher than the elastic limit inherent in said sheet when the fillets are formed merely by bending the metal. 10. A fluted, tubular shaft having swaged compression formedfillets in a wall of varying thickness made of plate metal of 11 gauge 4 and thicker.

11. A fluted, tubular' shaft having swaged compression formed fillets in a wall made of plate metal of 11 gauge and thicker.

12. A tapered, fluted, tubular pole. made i of plate metal of 11 gauge andthicker with swaged compression formed fillets.

CARL A. FRAHM. EDMUND WV. RIEMENSCHNEIDER. 

